Colorful liquid crystal thin film, method of manufacturing thereof and display device

ABSTRACT

The disclosed technology relates to a colorful liquid crystal thin film, a method of thereof and a display device. An embodiment of the method of manufacturing a colorful liquid crystal thin film comprises: adjusting a voltage applied across a liquid crystal cell filled with blue phase liquid crystal until the liquid crystal cell shows a required color; and radiating a portion of the liquid crystal cell needed to show the required color by ultraviolet rays.

BACKGROUND

One or more embodiments of the disclosed technology relates to acolorful liquid crystal thin film, a method of thereof and a displaydevice.

Currently, the technology for the flexible display is graduallyadvanced. The colorful liquid crystal thin film is formed of acholesteric liquid crystal material in most flexible display devices. Amethod for forming a colorful liquid crystal thin film by using acholesteric liquid crystal material comprising the following steps.

Step S101 of rendering the liquid crystal thin film to show a red colorby setting the temperature to a first temperature. The first temperatureis about 25° C., for example.

Step S102 of radiating the region needed to be manufactured as a redregion by ultraviolet irradiation to fix liquid crystal in this region,as shown in FIG. 1.

Step S103 of rendering the liquid crystal thin film in a region whereliquid crystal is not fixed to show a green color by setting thetemperature to a second temperature. The second temperature is about 34°C., for example.

Step S104 of radiating a region needed to be manufactured as a greenregion by ultraviolet irradiation to fix the liquid crystal in thisregion, as shown in FIG. 2.

Finally, the liquid crystal thin film with red and green colors ismanufactured.

SUMMARY

An embodiment of the disclosed technology provides a method ofmanufacturing a colorful liquid crystal thin film, comprising: adjustinga voltage applied across a liquid crystal cell filled with a blue phaseliquid crystal until the liquid crystal cell shows a required color; andradiating a portion of the liquid crystal cell needed to show therequired color by ultraviolet rays.

Another embodiment of the disclosed technology provides a colorfulliquid crystal thin film, comprising: substrates; and a mixture of apolymerizable blue phase liquid crystal and a photoinitiator uniformlycoated on one of the substrates, wherein a pitch of the mixture of thepolymerizable blue phase liquid crystal and the photoinitiator isadjusted to a required pitch under an applied electrical field and thenis fixed by ultraviolet radiation so that the colorful liquid crystalthin film shows the required color.

Further another embodiment of the present disclosed technology providesa display device, comprising: an array substrate; an opposing substrate;and a colorful liquid crystal thin film, interposed between the arraysubstrate and the opposing substrate, wherein the colorful liquidcrystal thin film is the colorful liquid crystal thin film according toan embodiment of the disclosed technology.

Further scope of applicability of the disclosed technology will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the disclosedtechnology, are given by way of illustration only, since various changesand modifications within the spirit and scope of the disclosedtechnology will become apparent to those skilled in the art from thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technology will become more fully understood from thedetailed description given hereinafter and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the disclosed technology and wherein:

FIG. 1 is a principle view of manufacturing the colorful liquid crystalthin film in the related art;

FIG. 2 is a principle view of manufacturing the colorful liquid crystalthin film in the related art;

FIG. 3a -FIG. 3j are a schematic views for showing states during aprocess of manufacturing the red, green and blue liquid crystal thinfilm according to an embodiment of the disclosed technology; and

FIG. 4 is a schematic structural view of the colorful liquid crystalthin film according to an embodiment of the disclosed technology.

DETAILED DESCRIPTION

One or more embodiments of the disclosed technology being thusdescribed, it will be obvious that the same may be varied in many ways.Such variations are not to be regarded as a departure from the spiritand scope of the disclosed technology, and all such modifications aswould be obvious to those skilled in the art are intended to be includedwithin the scope of the accompanying claims.

The inventors has found that, in the traditional manufacturing processof a colorful liquid crystal thin film, it is difficult to exactlycontrol the temperature and manufacture the colorful liquid crystal thinfilm with standard colors, the manufacturing efficiency is relativelylow and the number of the colors is relatively small.

Blue phase is a phase that is between a liquid crystal phase and anisotropy state, and a blue phase liquid crystal can show some colors inthe range of visible light blue phase liquid crystals can be dividedinto small molecular blue phase and polymer blue phase liquid crystals,in which polymer blue phase liquid crystals have gotten more attentionbecause wide stable range.

Embodiments of the disclosed technology provide a colorful liquidcrystal thin film, a method of manufacturing the colorful liquid crystalthin film, and a display device. The colorful liquid crystal thin filmcan be manufactured with a polymer-stabilized blue phase liquid crystal,the liquid crystal can be twisted under applied electric fields to showdifferent colors and then fixed by ultraviolet radiation. In anembodiment of the disclosed technology, it is easier to twist liquidcrystal molecules under applied electric fields than by controlling thetemperature, thus the manufacturing efficiency of the colorful liquidcrystal thin film can be improved and it is easy to control colors thatthe colorful liquid crystal thin film is intended to show. In addition,in the embodiments of the disclosed technology, the colorful liquidcrystal thin film with more kinds of colors can be manufactured byapplying different electric fields.

A method for manufacturing a colorful liquid crystal thin film accordingto an embodiment of the disclosed technology comprising the followingsteps.

Step S401 of adjusting a voltage applied across a liquid crystal cellfilled with a blue phase liquid crystal material until the liquidcrystal cell show a required color; and

Step S402 of radiating a portion needed to show the required color inthe liquid crystal cell by ultraviolet radiation to fix the liquidcrystal.

Because the blue phase liquid crystal can be twisted under an appliedelectric field to make the color of the light transmitted through theliquid crystal changed, the liquid crystal cell can show a desired colorby adjusting the voltage applied across the liquid crystal cell filledwith the blue phase liquid crystal, and then, the pitch of the liquidcrystal can fixed by radiating the liquid crystal with ultravioletradiation so that when the electric field is removed, the colorfulliquid crystal thin film still show the required color in the regionintended to show the desired color.

The applied voltage may be in the range of 30˜100V, for example; thevalue of the voltage may be proportional to the content of chiralitygroups in polymerization monomers. With increase of the content ofchirality groups, the polymerization system may appear in blue, green,and red colors, for example. In one example, when the content ofchirality groups in the system is 18˜22%, 23˜27%, and 28˜30%, the systemmay appear in blue, green, and red, respectively.

With respect to the different kinds of blue phase liquid crystalmaterials, the voltages of the applied electric field for rendering thecolorful liquid crystal thin films to show a same color may bedifferent, thus in operation, the voltages can be adjusted by graduallyincreasing or decreasing until the liquid crystal cell shows a requiredcolor. In addition, with regard to a certain kind of blue phase liquidcrystal materials, a voltage range may be determined based on operationexperience in order to decrease the time needed to adjust the voltages,so that the efficiency of manufacturing the colorful liquid crystal thinfilm can be improved.

Further, in order to fix the pitch of a blue phase liquid crystalmaterial to the currently required pitch after the liquid crystal cellshows the required color and make a color of the liquid crystal cell tobe closer to the required color, the period and intensity for theultraviolet irradiation can be determined by tests. More preferably, amercury lamp may be used to radiate the portion of the liquid crystalcell required to show the currently required color before theultraviolet irradiation is used to radiate the portion of the liquidcrystal cell. Thus, the pitch of the blue phase liquid crystal may bequickly fixed to the currently required pitch during the mercury lampradiation; then, by radiating ultraviolet rays, the blue phase liquidcrystal molecules can be polymerized to fix the liquid crystal.

In an example, after the mercury lamp is radiated for about 5-15minutes, an initial fixing of the liquid crystal material is completed;and more preferably, the mercury lamp radiation time is about 10minutes, and the fixing effect is better.

When the ultraviolet ray or the mercury lamp is used to radiate aportion of the liquid crystal cell required to show a required color,the portion of the liquid crystal cell required to show the currentlyrequired color can be exposed but the rest portion of the liquid crystalcell ca be covered or shield for example, and thus, the ultraviolet raysor the mercury lamp may radiate total liquid crystal cell and liquidcrystal in the portion of the liquid crystal cell required to show thecurrently required color can be fixed. For example, a prepared mask canbe used to cover the rest portion of the liquid crystal cell.

In an embodiment of the disclosed technology, a method for filling ablue phase liquid crystal into a liquid crystal cell comprises thefollowing steps.

Step S501 of mixing a polymerizable blue phase liquid crystal and aphotoinitiator, heating the mixture to a clear point and then cooling.For example, the mixture may be cooled to a room temperature and then isprepared for usage.

Step S502 of providing by coating uniformly the mixture of thepolymerizable blue phase liquid crystal and the photoinitiator on aglass substrate. This glass substrate may be a conductive glasssubstrate formed with electrode patterns. Further, other kinds ofsubstrate such as plastic substrates and silica substrates can be used.

In one example, the polymerizable blue phase liquid crystal may be, forexample, formed by processing a blue phase liquid crystal to havepolymerizability. In another example, the polymerizable blue phaseliquid crystal may be formed by mixing a blue phase liquid crystal and areactive mesogen (RM).

Any common photoinitiator, such as, Irgacure 651, may be used as thephotoinitiator in the method, or any other kind of photoinitiator may beselected based on the practice and tests.

A polymerizable blue phase liquid crystal may comprises polymerizabledouble bond, triple bond, or other groups (e.g., carboxyl, hydroxy,amino group, etc.), and can undergo a polymerization action to form astable system under the effect of an photoinitiator. The blue phaseliquid crystal system includes polymerizable groups, chirality groups,rigid structures, and flexible structures. For example, thepolymerizable groups and chirality groups may be contained in the rigidstructures and flexible structures. A photoinitiator can absorb energyat a certain wavelength for example in the ultraviolet light range(250˜420 nm) or visible light range (400˜800 nm) to generate freeradicals, positive ions, etc to trigger polymerization and crosslinkingof monomers.

The examples of the polymerizable functional groups (PFG) in the bluephase liquid crystal system may include HOOC—(CH₂)_(n)—, NH₂—(CH₂)_(n)—,HO—(CH₂)_(n)—, HC═CH—(CH₂)_(n)—, HC≡C—(CH₂)_(n)—, and so on.

The examples of the rigid structure (RS) may include

and the like or other stable chemical structure with rigid propertiesand containing 5- or 6-membered rings or combination thereof.

Chiral group (CG) refers to a general class of substances with a chiralstructure, which can be a natural compound with chirality such ascholesterin

and derivates thereof, peppermint camphor

and derivates thereof, or a synthesized compound designed to have achiral centre.

As discussed above, the basic structure of the mentioned blue phasemolecule can be designed as follows: FG-RS-CG, (FG: flexible group).Since PFG can be included in RS or FG, and CG can be in FG, PFG or agroup thereof, the order of RS and CG as well as the chemical bondsconnected thereto can be varied. In another example, the abovefunctional groups can be present in the different molecules, one or moreof which contain the liquid crystal molecules, and exhibit theproperties of a blue phase liquid crystal when mixing.

In step S502, spin-coating may be used to coating uniformly the mixtureof the polymerizable blue phase liquid crystal and the photoinitiator ona glass substrate. Generally, an upper substrate, a lower substrate andthe blue phase liquid crystal mixture filled between the substratesconstitutes a liquid crystal cell. For example, preferably, a width ofthe liquid crystal cell is not more than 10 μm, and the width may be ina range of 3 μm-6 μm. The upper and lower substrates may be conductiveglass substrate.

Hereinafter, an example of the method for manufacturing the colorfulliquid crystal thin film according to an embodiment of the disclosedtechnology, the method comprising the following steps.

Step S601 of mixing a polymer-stabilized blue phase liquid crystal(e.g., right-handedness), an RM and a photoinitiator (e.g.,Irgacure651), heating the mixture to a clear point and then cooling;

Step S602 of spin-coating the mixture obtained in step S601 on aconductive glass substrate, wherein a width of each of upper and lowersubstrates is 3 μm-6 μm for example;

Step S603 of applying a voltage across the liquid crystal cell andadjusting the voltage of the liquid crystal cell to make the liquidcrystal cell to show a red color, as shown in FIG. 3 a;

Step S604 of covering a mask on the liquid crystal cell and exposing theregion required to show the red color, and radiating the liquid crystalcell for 10 minutes for example with a mercury lamp to fix the pitch ofthe liquid crystal in the red region, as shown in FIG. 3 b;

Step S605 of radiating the liquid crystal cell by ultraviolet radiationto promote the polymerization of RM for fixing the liquid crystal in theregion required to shown the red color, as shown in FIG. 3 c;

Step S606 of stopping applying the voltage until other region returns toa clear state for example the initial state, as shown in FIG. 3 d;

Step S607 of applying another voltage to the clear region to show agreen color, as shown in FIG. 3 e;

Step S608 of covering another mask on the liquid crystal cell andexposing the region required to show the green color, and radiating theliquid crystal cell for 10 minutes for example with a mercury lamp tofix the pitch of the liquid crystal cell in the green region;

Step S609 of radiating the liquid crystal cell by ultraviolet radiationto promote the polymerization of RM in order to fix liquid crystal inthe green region, as shown in FIG. 3 f;

Step S610 of stopping applying the voltage until other region (otherthan the red, green regions) returns into a clear state for example aninitial state, as shown in FIG. 3 g;

Step S611 of applying further another voltage to the clear region toshow a blue color, as shown in FIG. 3 h;

Step S612 of covering further another mask on the liquid crystal celland exposing the region required to show the blue color, and radiatingthe liquid crystal cell for 10 minutes for example with a mercury lampto fix the pitch of the liquid crystal cell in the blue region;

Step S613 of radiating the liquid crystal cell by ultraviolet radiationto promote the polymerization of RM in order to fix liquid crystal inthe blue region, as shown in FIG. 3i ; and

Step S614 of stopping to apply the voltage and obtaining a colorfulliquid crystal thin film with red, green and blue colors, as shown inFIG. 3 j.

Further an embodiment of the disclosed technology provides a colorfulliquid crystal thin film, the colorful liquid crystal thin film ismanufactured by a method according to an embodiment of the disclosedtechnology, as shown in FIG. 4, for example. The colorful liquid crystalthin film comprising: conductive glass substrates 801; a mixture 802 ofa polymerizable blue phase liquid crystal and a photoinitiator uniformlyprovided on one of the conductive glass substrates 801. In addition, thepitches of the mixture of the polymerizable blue phase liquid crystaland the photoinitiator have become the required pitches and then arefixed by ultraviolet radiation.

The polymerizable blue phase liquid crystal may be formed, for example,by processing a blue phase liquid crystal to have polymerizability or bymixing the blue phase liquid crystal and RM (reactive mesogen).

In another embodiment of the disclosed technology, a display device isprovided, and the display device comprises a colorful liquid crystalthin film provided by an embodiment of the disclosed technology, and thedisplay device may be a liquid crystal display or another kind ofdisplay devices. The display device comprises an array substrate and anopposing substrate, wherein the colorful liquid crystal thin film isprovided between the array substrate and the opposing substrate, anddriving elements are disposed on the array substrate.

One or more embodiments of the disclosed technology provide a method ofmanufacturing a colorful liquid crystal thin film, a colorful liquidcrystal thin film and a display device. The colorful liquid crystal thinfilm is manufactured by a polymer-stabilized blue phase liquid crystal,the liquid crystal can be twisted under applied electric fields in orderto show different colors and then fixed by ultraviolet radiation. Theliquid crystal can twisted under the electric fields, the control of theelectric fields are easier than the control of the temperatures, so themanufacturing efficiency of the colorful liquid crystal thin film can beimproved and it may be easy to control the color of a color of thecolorful liquid crystal thin film. In addition, the colorful liquidcrystal thin film with more colors can be manufactured by applying thedifferent electric field.

The embodiment of the disclosed technology being thus described, it willbe obvious that the same may be varied in many ways. Such variations arenot to be regarded as a departure from the spirit and scope of thedisclosed technology, and all such modifications as would be obvious tothose skilled in the art are intended to be included within the scope ofthe following claims.

What is claimed is:
 1. A method of manufacturing a colorful liquidcrystal thin film, comprising: adjusting a voltage applied across aliquid crystal cell filled with a blue phase liquid crystal until theliquid crystal cell shows a first required color; radiating a firstportion of the liquid crystal cell needed to show the first requiredcolor by a mercury lamp and then radiating the first portion of theliquid crystal cell needed to show the first required color byultraviolet rays, while the voltage is maintained across the liquidcrystal cell, a pitch of the blue phase liquid crystal in the firstportion of the liquid crystal cell being adjusted and fixed accordingly;suspending applying the voltage across the liquid crystal cell until aremaining portion of the liquid crystal cell returns to a clear state,while the first portion of the liquid crystal cell shows the firstrequired color; reapplying and adjusting the voltage across the liquidcrystal cell until the remaining portion of the liquid crystal cellshows a second required color, while the first portion of the liquidcrystal cell shows the first required color; and radiating a secondportion of the liquid crystal cell needed to show the second requiredcolor by ultraviolet rays, the second portion being at least part of theremaining portion of the liquid crystal cell.
 2. The method according toclaim 1, wherein the radiating the first portion of the liquid crystalcell needed to show the first required color by the ultraviolet rayscomprises: exposing the first portion of the liquid crystal cell neededto show the first required color and covering the remaining portion; andradiating the liquid crystal cell with the ultraviolet rays.
 3. Themethod according to claim 1, wherein the radiating the first portion ofthe liquid crystal cell needed to show the first required color by themercury lamp comprises: exposing the first portion of the liquid crystalcell needed to show the first required color and covering a restportion; and radiating the liquid crystal cell by the mercury lamp. 4.The method according to claim 1, wherein the radiating the first portionof the liquid crystal cell needed to show the first required color bythe mercury lamp comprises: radiating the first portion of the liquidcrystal cell needed to show the first required color by the mercury lampfor 5-15 minutes.
 5. The method according to claim 1, furthercomprising: manufacturing the liquid crystal cell filled with the bluephase liquid crystal.
 6. The method according to claim 5, wherein themanufacturing the liquid crystal cell filled with the blue phase liquidcrystal comprises: mixing a polymerizable blue phase liquid crystal anda photoinitiator, heating the mixture to a clear point and then cooling;and providing the mixture of the polymerizable blue phase liquid crystaland the photoinitiator on a substrate.
 7. The method according to claim6, wherein the substrate is a conductive substrate.
 8. The methodaccording to claim 6, wherein the polymerizable blue phase liquidcrystal is formed by processing the blue phase liquid crystal to havepolymerizability or by mixing the blue phase liquid crystal and areactive mesogen.
 9. The method according to claim 7, wherein thepolymerizable blue phase liquid crystal is formed by processing the bluephase liquid crystal to have polymerizability or by mixing the bluephase liquid crystal and a reactive mesogen.
 10. The method according toclaim 1, wherein the first required color is red or green.